Continuously variable hydrofoils for papermaking wires



Feb. 24,1970 R. c. CLARK 3,497,420

CONTINOUSLY VARTBLE HYDROFOILS FOR PAPERMAKING WIRES Filed Jah. `so, 1967 f /5 fZ/ /7 Z United States Patent O 3,497,420 CONTINUOUSLY VARIABLE HYDROFOILS FOR PAPERMAKING WIRES Raymond C. Clark, Orange, Conn., assignor to Huyck Corporation, Rensselaer, N.Y., a corporation of New York Filed Jan. 30, 1967, Ser. No. 612,644 Int. Cl. D21f 1/48 U.S. Cl. 162-352 8 Claims ABSTRACT OF THE DISCLOSURE A stationary drainage element for a papermaking machine having a flexible diaphragm means enclosing a cavity to which a vacuum or pressurized air may be supplied in order to change the configuration of the ilexible diaphragm means and vary the angle at which the flexible means diverges from the forming medium traveling over the drainage element.

BACKGROUND OF THE INVENTION In a Fourdrinier papermaking machine, an aqueous suspension of fibers, called the furnish, is deposited on a moving forming medium. As the furnish is moved along by the forming medium, much of the Water is removed therefrom and a somewhat self-supporting web is formed. Subsequent to formation, the web is compacted and further dewatered by passing it between a series of press rolls, after which it is dried to its finished condition. During the initial forming stage, it is essential that the furnish be adequately drained so that the finished web is of desired quality and of suitable strength to permit further processing. It is also desirable to remove substantial amounts of Water from the web during the forming stage because it is much cheaper to do so during the forming stage than through the application of heat, for example, during the dryer operations.

In order to accompilsh this dewatering, table rolls and/ or high vacuum boxes have been utilized. However, as the technical literature shows, table rolls have a sharp vacuum gradient which may cause premature formation of the web and which may create liquid throwback, causing rewetting of the web. Suction boxes, due to the large amount of vacuum required for their operation can only be utilized where the web is already somewhat formed. Further, suction boxes greatly increase the wear of the forming medium. Thus alternate means have been sought for dewatering the web during the forming stages.

One solution to this problem is to utilize a stationary deflector, commonly referred to as a hydrofoil, positioned under the forming medium and in contact with the under surface thereof. One example of such a device is shown in U.S. Patent No. 2,928,465. Since the trailing surface of the hydrofoil diverges from the forming medium, the movement of the forming medium over the hydrofoil produces a hydrodynamic suction at the underside of the forming medium and causes water to be drawn from the web through the forming medium with such a device, a more uniform vacuum gradient is set up across the web than with the aforementioned table rolls and/or suction boxes. However, in order to vary the amount of dewatering obtained by a hydrofoil, it is generally necessary to vary the running speed of the papermaking machine or to change the angle by which the trailing edge of the hydrofoil diverges from the forming medium in the direction of travel. Since it is generally undesirable economically to vary the running speed of the papermaking machine, and since the Water removal capacity of the press and dryer sections impose upper limits on the speeds at which such machines can operate, as a practical matter the machine operator is restricted to varying the amount of suction pressure in the region of the diverging portion of the hydrofoil, which the operator may do by changing the angle of divergence of the trailing surface of the hydrofoil in order to vary the drainage rate.

In present day hydrofoil arrangements, the machine operator must mechanically adjust various linkages in order to change the angle of divergence of the trailing surface of the hydrofoil or alternately replace one hydrofoil blade with another having a trailing surface oriented at a different angle of divergence. These methods not only require a mechanical skill and finesse, but may also require machine shut-down until the adjustments are completed. As this is both time-consuming and costly, alternate methods have been sought for varying the dewatering or drainage rate of hydrofoils.

Therefore, one object of the present invention is to provide an improved hydrofoil for papermaking machines.

Another object of the present invention is to provide an improved variable hydrofoil for use in papermaking machines.

Still another object of the present invention is to provide means for continuously varying the dewatering eiect of a hydrofoil.

A further object of the present invention is to provide' means for continuously varying the angle of divergence between the trailing surface of a hydrofoil and the forming medium in a papermaking machine.

A further object of the present invention is to provide means for varying the configuration of the trailing surface of a hydrofoil for use in a papermaking machine.

SUMMARY OF THE INVENTION In one embodiment of the present invention, there is included in a papermaking machine a stationary drainage element disposed in supporting relationship to the forming medium and extending across the machine transversely to the direction of travel of the forming medium. The stationary drainage element has a leading edge, a central supporting surface in engagement with the forming medium, and a trailing portion having a cavity or other similar open-ended surface. Flexible means enclose the cavity and provide a trailing surface of the hydrofoil, and means are provided for supplying a change in pressure to the cavity. By selective application of either a vacuum or pressurized air to the cavity, it is possible to vary the configuration of the trailing surface of the hydrofoil. Thus, it is possible to vary the angle at which trailing surface of the flexible means diverges from the forming medium and also the configuration of the trailing surface. As such, the dewatering rate of a hydrofoil may readily be controlled.

Additional objects and advantages of the present invention together with a better understanding thereof may be had by referring to the following detailed description of the present invention together with the accompanying drawings.

DESCRIPTION OF DRAWINGS FIGURE 1 is a cross-section view of a stationary drainage element constructed in accordance with the principles of the present invention, no vacuum being applied to the enclosed cavity;

FIGURE 2 is a cross-section view of the stationary `drainage element shown in FIGURE 1, a partial vacuum being applied to the enclosed cavity;

FIGURE 3 is a cross-section view of the stationary drainage element shown in FIGURE l, the maximum vacuum being applied to the enclosed cavity;

FIGURE 4 reveals an alternate embodiment of the stationary drainage element shown in FIGURE l; and

FIGURE 5 is a cross-section view of the stationary drainage element shown in FIGURE 4 and further including means for providing feedback to a system for automatically controlling the position of the trailing edge of the hydrofoil.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, there is shown a portion of the forming section of a papermaking machine including a forming medium 5 which is traveling from left to right as viewed in the drawing. It should be noted that the forming medium may be of a wire construction, of a synthetic material such as shown and described in U.S. Patent No. 2,903,02l-Holden et al., or of any other suitable construction. One or more stationary hydrofoil elements 7 are disposed beneath the forming medium 5 and in engagement with the underside of the forming medium so as to provide support therefor. The hydrofoil elements 7 are oriented transverse to the path of travel of the forming medium 5 and they may be constructed of stainless steel, polyethylene, or other material suitable for such a use.

Each hydrofoil element 7 includes a central portion 11 having a surface in supporting relationship to the forming medium 5 and a trailing portion 13 having a surface which diverges from the forming medium 5 so as to produce a suction on the forming medium 5 as the forming nedium travels thereover. The leading edge 9 of the hydrofoil element 7 acts as a doctor blade to remove water clinging to the underside of the forming medium 5 and, in order to increase the amount of water removed, the leading edge 9 preferably is acutely angled with respect to the forming medium 5. Besides providing means for supporting the forming medium 5, the central portion 11 of the hydrofoil element 7 also provides a seal which is advantageous in the operation of the hydrofoil 7, this being explained more fully hereinafter. The central portion 11 of the hydrofoil element 7 is generally fiat in order to reduce the possibility of web jump as the forming medium travels thereover.

The trailing portion 13 of the hydrofoil 7, that portion 3f the hydrofoil which sets up a hydrodynamic suction on the forming medium 5, includes a cavity 15 or other similar open-ended structure enclosed by exible means. The flexible means comprises a resilinet diaphragm 17 or )ther similar material having a surface which is, during peration, at least partly in engagement with the under- ;ide of the forming medium 5. The diaphragm 17 corn- ;rises the trailing surface of the hydrofoil. Note that the liaphragm 17 must be of a deformable material, for example, an elastomeric material. As such, polymeric mateials such as rubber or rubber-like substances have been found generally desirable for use in their construction as hey are resistant to the wear of the forming medium and lave a relatively low coefficient of friction. However, hese materials are given by way of example only as it is rot the intention of the present invention to be limited o such materials.

Either a vacuum or pressurized air may be supplied to the cavity 15 in order to vary or change the pressure within the cavity 15. In the preferred embodiment of the present invention, a vacuum is supplied to the cavity 15; however, a pressure pump may also be utilized to vary the pressure within the cavity. When a vacuum (or pressurized air) is supplied to the cavity, it is possible to vary the configuration of the flexible diaphragm 17 and the angle at which the upper surface of the flexible diaphragm 17 diverges from the forming medium 5. By varying the configuration of the flexible diaphragm 17 and the angle at which the upper surface of the flexible diaphragm 17 diverges from the forming medium 5, it is possible to control the drainage rate of the hydrofoil-7. To achieve this, means Vare provided for supplying a vacuum (or pressurized air) to the enclosed cavity 15. In this instance, the means comprises an annular opening 19 which is used to connect the enclosed cavity 15 with a suitable pump (not shown, as such pumps are old).

Movement of the forming medium 5 over the hydrofoil element 7 creates a zone of suction 21 under the forming medium 5, the position of the suction zone along the hydrofoil being determined by the configuration of the diaphragm 17. If the leading edge 9 of the hydrofoil 7 is not sealed, the suction zone 21 may draw air into the zone from the leading edge of the hydrofoil, thus decreasing the efficiency of the hydrofoil in drawing water from the furnish. Therefor, the use of the central portion 11 of the hydrofoil 7 which, due to the forming medium 5 being in contact therewith, tends to prevent air from being drawn in over the leading edge 9 into the suction zone of the hydrofoil and ensures that a maximum suction will be applied to the forming medium for dewatering purposes.

It can be seen in FIGURE l that when no vacuum is applied to the enclosed cavity 15, the flexible diaphragm 17 will assume a normal configuration, this generally being determined by the physical properties of the particular material(s) used for the diaphragm, the amount of suction and the weight of water coming over it. By applying a vacuum to the enclosed cavity 15, the configuration of the fiexible diaphragm 17 is made to change. By selective application of the vacuum to the cavity 15, it is possible to control the configuration of the diaphragm 17 and the drainage effect of the hydrofoil element 7.

FIGURE 1 shows the flexible diaphragm 17 with no vacuum applied to the enclosed cavity 15, the resulting suction zone being located at the extreme right edge of the diaphragm 17 FIGURE 2 shows the flexible diaphragm 17 with a partial vacuum applied to the cavity 15, the resulting suction zone being located centrally along the diaphragm 17. Note the change in configuration of the diaphragm and particularly the point and angle at which it diverges from the forming medium 5.

FIGURE 3 reveals the maximum vacuum applied to the enclosed cavity 15, the resulting suction zone being located at the left edge of the diaphragm 17. Again, this shift results in a change in both the configuration of the diaphragm and the point at which the diaphragm diverges from the forming medium. Further, and depending upon the particular materials used to make the diaphragm, the amount of suction applied and the weight of water, the suction zone 21 will be of either increased or decreased intensity; this being determined by the angle and configuration of the diaphragm as it diverges from the forming medium for a given forming medium speed.

It should ibe noted that when pressurized air rather than a vacuum is supplied to the cavity 15, the cavity 15 then being at a pressure greater than the surrounding atmosphere, the relative positions of the suction zone will be exactly the reverse of those discussed in FIGURES l-3. Further, the diaphragm will assume a somewhat convex configuration rather than the concave configuration shown in FIGURES 1-3. That is, no pressurized air supplied to the cavity, the suction zone will be located at the left ed-ge of the diaphragm 17 whereas with maximum air pressure supplied to the cavity, the suction zone will be located at the right edge of the diaphragm 17.

Further, it is possible that both pressurized air and a vacuum may be used to control movement of the diaphragm over its entire range. That is, under normal or no pressure conditions, the diaphragm will assume a general configuration with the suction zone located centrally along the cavity 15. If it is desired to shift the suction zone to the right edge of the cavity, then pressurized air is introduced into the cavity 15 until the configuration of the diaphragm is somewhat similar to that shown in FIGURE 1. If it is desired to shift the suction zone to the left edge of the cavity 15, then a vacuum would be applied to the cavity 15 until the configuration of the diaphragm is similar to that shown in FIGURE 3.

Turning now to FIGURE 4, there is shown a hydrofoil element 7 similar to that shown and discussed in FIG- URES 1-3; however, the flexible means is made of a resilient metal. In this arrangement, it is generally desirable to vary only the angle at which thediaphragm diverges from the forming medium and to hold the configuration of the hydrofoil relatively constant. The metal diaphragm 17A is mounted to the central portion 11 of the hydrofoil 7, for pivotable movement thereabout, as -by brazing or bonding. The trailing edge 30 of the metal diaphragm 17A may be bent at right angles with respect to the main portion thereof and is connected to the trailing edge 13 by suitable sealing means 31 such as a polymeric material, rubber or rubber-like materials being preferred. A stop member 29 is positioned within the enclosed cavity 15 to limit the deection of the metal diaphragm 17A. The stop member 29 may also be made to control the shape of the diaphragm 17A. In order to further the latter purpose of the stop member 29, a plurality of stop members 29 (shown by dotted outline in FIGURE 4) may be so positioned and arranged within the cavity 1S and that the diaphragm will assume a predetermined configuration when a vacuum is applied to the cavity. That is, the vacuum will cause the diaphragm 17A to be drawn against the stop members 29 so that the diaphragm 17A assumes a general configuration which will be determined by the placement and sizing of each of the individual stop members 29. Note that this feature may also be used with the non-metal exible diaphragms 17 discussed in FIGURES 1-3. When a metal diaphragm is utilized, application of a vacuum to the cavity 1S will cause the metal diaphragm 17A to pivot about the point where it is joined to the central portion 11 of the hydrofoil 7. Such a construction provides avariable pitch hydrofoil element and may be utilized in installations Vwhere it is desired to maintain the upper surface of the hydrofoil in a straight-edge conguration. Further application of a vacuum will cause the diaphragm to assume a coniiguration in accordance with the preceding discussion.

Turning now to FIGURE 5, there is shown a further embodiment of the present invention in which there is shown a hydrofoil element 7 which includes means enabling automatic control of the configuration of the diaphragm. Specifically, there is shown a diaphragm 37 having an aperture 39 therein. One end of a hollow exible helical tube 41 is connected to the aperture 39, the opposite end of the tube 41 being connected to a comparator control system 35 or the like.

The comparator control system 35 may be of the type that compares a monitored signal to a reference signal and in response to deviation of the monitored signal from the reference signal, provides an error or deviation signal which is in proportion to the diiierence between the monitored and reference signals. This error signal is then used to provide correction for the system. However, such a system is given by way of example only and is not the intention of the present invention to be limited thereto.

In the present instance, as the forming medium 5 passes over the hydrofoil 7, a suction zone is created therebetween, and a signal proportional to the value of the suction zone is supplied through the hollow tube 41 to the comparator. If the suction zone created varies from that which is desired, an error signal will be produced by the comparator and supplied to the means for controlling the vacuum pump (shown only as the vacuum pump control). In accordance with this error signal, the amount of vacuum supplied to the cavity 15 would be changed, thus varying the configuration of the diaphragm 17 and reorienting the suction zone of the hydrofoil. When the suction zone is at the desired value, the comparator will sense zero deviation from the reference signal and will maintain the appropriate amount of vacuum supplied to the cavity.

Thus, automatic control of the hydrofoil 7 can fbe achieved without the elaborate mechanisms and linkages previously required `for similar adjustments. Further, an automatic system for controlling the hydrofoils may be arranged in which the machine operator will only have to set the machine for the desired suction zone and then the machine itself will adjust itself to that desired level.

It should be noted that it is not the intention of the present invention to be limited to a single hydrofoil element. As such, a plurality of individual hydrofoil units may be combined to form a multiple blade unit. Also, it should be restated that it is the intention of the presentinvention to include devices which operate on a vacuum, a source of pressurized air, or both and that where vacuum has been used throughout the specification, it is t0 be understood that the term pressurized air or other similar terminology could have been substituted therefor without departing from the scope of the present invention.

What I claim as new and novel and desire to secure by Letters Patent of the United States is:

1. A stationary drainage element for a papermaking machine disposed in supporting relationship to the forming medium and extending transverse to the direction of travel of the forming medium, said drainage element having a leading edge and a trailing portion including a cavity, flexible means sealingly enclosing said cavity, said iiexible means having a surface which diverges from the forming medium at an angle, and means for supplying a change to the pressure within said cavity to vary the configuration of said flexible means and to vary said angle at which said surface diverges from the forming medium.

2. A stationary drainage element for a papermaking machine disposed in supporting relationship to the forming medium and extending transverse to the direction of travel of the forming medium, said drainage element having a leading edge, a central portion in supporting engagement with the forming medium, and a trailing portion including a cavity, flexible means sealingly enclosing said cavity and having a surface which diverges from the forming medium at an angle, at least a portion of said surface being in engagement with the underside of the forming medium, and means for supplying a change to the pressure within said enclosed cavity to vary the configuration of said flexible means and to vary said angle at which said surface diverges from the forming medium.

3. A stationary drainage element as described in claim 2 wherein said exible means is made of a polymeric material.

4. A stationary drainage element as described in claim 3 wherein said flexible means is made of an elastomeric material.

5. A stationary drainge element as described in claim 2 wherein said surface of said flexible means comprises a metal diaphragm.

6. A stationary drainage element as described in claim 2 wherein said flexible means includes an aperture, and further including means for connecting said aperture to Imeans for regulating the amount of pressure change supplied to said enclosed cavity.

7. A stationary drainage element as described in claim 6 wherein said connecting means comprises a hollow tube.

8. A stationary drainage element as described in claim 2 further including at least one stop means disposed Within said cavity against which the flexible means may be drawn to cause said surface of said flexible means change in pressure Within said cavity.

References Cited UNITED STATES PATENTS S. LEON BASHORE, Primary Examiner R. H. TUSHIN, Assistant Examiner Us. C1; XR. 162-252, 374 

